


Promissum

by Yunica



Series: Pueritia Amicus [5]
Category: Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Alternate Universe - Canon Divergence, Alternate Universe - Childhood Friends, Byleth is unamused, Byleth wants to be a Knight for Edelgard, Edelgard finally picking up an axe, Training, Young Dimitri is a clumsy
Language: English
Status: Completed
Published: 2020-01-05
Updated: 2020-01-05
Packaged: 2021-02-27 11:01:48
Rating: Not Rated
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,659
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/22126030
Author URL: https://archiveofourown.org/users/Yunica/pseuds/Yunica
Summary: A promise to stay together even after, and a promise to protect her.
Relationships: Edelgard von Hresvelg & My Unit | Byleth
Series: Pueritia Amicus [5]
Series URL: https://archiveofourown.org/series/1586014
Comments: 3
Kudos: 69





	Promissum

Edelgard asks Byleth to teach her how to wield a weapon. “Just in case I ever need to defend myself, and to make it easier on you. I don’t want to be a defenseless burden if I don’t have to be,” she said. Jeralt seems surprised that Edelgard wants to learn. He recommends showing Edelgard some basics first, and they start with the sword. Edelgard seems to have a knack for it, and she readily incorporates small things she has learned from simply watching Byleth practice. She approaches their training like she does everything else, with tenacious determination.

Despite how well their training goes, Byleth can tell that Edelgard is not as enamored with the sword as she herself is. They take to testing other weapons, trying to find one that interests Edelgard. The lance and bow are quickly discarded. The axe is next, and Byleth picks it up from the rack to hand to Edelgard. As soon as Edelgard wraps her hands around the handle, testing the weight, her eyes widen with wonder. They had clearly just found Edelgard another love.

Byleth shows her how to properly hold the axe, adjusts her form, and helps her perfect her swing. “It should arc like this, El. Otherwise it’ll be easy to deflect your swing.” Edelgard practices how to wield the weapon with an avid fever. The two of them practice in the courtyard every day, stretched out on the grass lining the courtyard whenever they take a break. Edelgard continues to improve each day, smiling proudly the first time she manages to disarm Byleth.

Oddly, Arundel has no issues with his niece swinging around a weapon, and even seemed to encourage it. He had stopped by to watch one of their sessions, hidden in the shadows. He only stepped out into the light once they finished for the day, applauding Edelgard’s progress and commending Byleth’s teaching. A man followed behind him, fully covered in black armor. Byleth eyes him warily, never having seen him before. Arundel spouts some prose that Byleth does not pay attention to before he and the man in the armor leave.

Edelgard re-racks the weapons as Byleth watches the two round the corner. Curious, Byleth asks, “Do you know who that man was?”

“He’s probably one of my uncle’s knights. He has too many to count, I don’t know what he needs them all for.”

“A knight? Are they normally hired by nobles?”

“Kind of. A knight is normally sworn to a noble, and they fight only for them.”

“So they fight because of loyalty and not because of gold.” Byleth moves to help Edelgard clean up. “How do you become a knight?”

“A certification is needed to be able to become a knight. At least that’s what one of my old lessons said.”

A thought churns, and Byleth imagines herself as a knight sworn to Edelgard. "Can anyone take the certification?"

"No, I think a noble has to support you, or you have to be a student of a school that has the tests.” Edelgard pauses in her tidying to look at Byleth. “Are you interested in becoming one, Byleth?”

"Hmm...I don't know." Fighting for a cause or for someone. It is an odd concept for Byleth, who grew up as a mercenary. If it was for _her_ though, Byleth could see the appeal.

“My uncle could probably help you take a certification. I know you would easily pass.”

Byleth does not want to swear anything to Arundel. “No, I don’t think I want to be a knight for your uncle.”

“Oh, then who?”

_You_. Byleth thinks, but instead says, “I don’t know.”

The idea of becoming a knight to stay by Edelgard's side continues to grow more and more appealing to Byleth as the days go by. She considers it so that she could still have a reason to stay beside Edelgard, regardless of if Arundel decided to continue hiring her and her father. It was a knight’s job to protect the noble they were sworn to, right? For Byleth, that would be no different than what she was already doing or willing to do.

It churns in her mind until Byleth finally brings it up to Edelgard one day while they are having lunch. “El, I want to become a knight."

"So you do want to become a knight?" Edelgard peers at her curiously.

"Yes. Your knight, so that I can stay with you."

Edelgard’s face flushes at the sudden and bold confession said with such nonchalance. “My knight? But I don’t think I’m able to help you with that right now. Maybe in the future...”

“It doesn’t have to be now or even soon, but someday, I promise to become your knight.” Byleth’s usual blank stare is unwavering.

Edelgard can still feel her face burning, but nods and vows, “Then, one day in the future, I promise to make you my knight.”

* * *

Byleth looks into the requirements to become a knight, and finds that there are multiple types of certifications that could be taken and passed. She only needed to pass one to qualify, and after some research, she knows which one she wants to take.

“You want to take flying lessons?”

“Yes, so that I can become a knight.”

“A knight? For Edelgard I assume?” Jeralt laughs, “With the way that girl swings an axe around, I don’t really think she needs a knight.”

Byleth deflates, “Oh…”

“Not that you can’t still be!” Jeralt is quick to rectify his statement and bring the conversation back to Byleth’s request. “You know you could take riding lessons instead, maybe I could even teach you. Don’t you want to be like your old man here?”

Byleth’s answer is immediate, head shaking. “No.”

“No?” Jeralt sounds betrayed.

“A pegasus allows for much more mobility and coverage of the battlefield. Your horse is too slow.”

“Too slow?! I’ll have you know that Fish is the fastest horse I’ve ever ridden. Don’t you remember all the times she’s gotten me across the battlefield in record time.” Fish, her father’s trusty steed. He had let Byleth name her when he discovered the horse years ago—around the time when he had first introduced fishing to Byleth.

“A pegasus will be able to carry me even faster than Fish.”

Her father defeatedly acqueises, and Byleth begins to take flying lessons.

* * *

Arundel calls for them to come inside and meet someone while they are out in the gardens. The boy in front of him has blonde hair, and looks to be around the same age as Edelgard. Her uncle introduces him as Dimitri. Arundel reminds—warns—them to be kind to Dimitri before he goes out the door as quickly as he came. Leaving them with a vague description that he was the son of a very important friend.

Dimitri is quiet, his eyes glued to the ground in front of him. Byleth stands farther back, watching him closely.

The three of them stand there until Edelgard decides to break the silence. “Hello Dimitri. My name is Edelgard.” She turns slightly to motion towards Byleth behind her, “and that is Byleth.” Dimitri chances a glance up after the introduction and catches Byleth’s piercing stare, and his eyes immediately dart back to ground nervously.

“Hello.” Dimitri mumbles it so softly that Edelgard barely hears it.

They lapse back into silence, and Edelgard glances back at Byleth, unsure what to do. Byleth shrugs, and then makes a motion of swinging an invisible blade. “Um, we were about to head into the courtyard. Would you like to come with us?”

Dimitri looks back up to Edelgard at the invitation. “Oh...s-sure!”

Dimitri trails behind them as they walk, and when they reach the courtyard, Byleth breaks off to grab their wooden weapons from the rack while Edelgard turns towards him. “Do you know how to use a weapon?”

“I’ve been practicing a little with swords and lances. My dad says that I should learn how to use them.”

“Byleth is very good with a sword. If you want, you could practice with her.”

“Oh no, that’s alright. I’ll just watch you guys.” Dimitri shrinks back a little at the offer.

“Okay. You can sit anywhere.” Edelgard accepts the axe from Byleth after seeing Dimitri take a seat on one of the benches lining the courtyard square. The two of them go through their normal routine, now as natural to them as breathing. First practicing individually on training dummies to warm up, and then coming together to spar a few rounds.

Byleth is as playful as she always in during their spars. Pressing in to force Edelgard on the defensive and then backing away to force her to give chase. “It’s an exercise that helps with preparing for both aggressive and nimble enemies,” Byleth had said with that small smile on her face. She disarms Edelgard again today, as she normally did, but still compliments her. “You’ve improved a lot, Edelgard. These spars are getting longer and longer each time. We might need to start setting a time limit for them.”

They both turn at the sound of applause, and find Dimitri watching them with wonder and interest. “You’re both amazing!”

Edelgard smiles, “Thank you. It must be because I have an excellent teacher.” Byleth grunts, brushing off the praise. “As you can see she is very shy.”

Dimitri laughs, and he seems more relaxed after that. He spends the rest of the day with them, and Byleth spends the whole time blatantly staring at him. It is only once the sun is starting to set that he decides he should head home. He disappears out the door with a promise to return tomorrow.

Edelgard prods Byleth, “I’m surprised you didn’t scare him off with how much you were staring.”

“He’s weird.”

“Weird can be good. Just like you.” Edelgard’s smile is mischievousness and fondness wrapped up in one. “He seems alright, and we do need to be nice to him.”

Dimitri shows up as promised the next day, and they spend the day in much the same way as before, him sitting on the sidelines again. He continues to show up the next day and the next, and Byleth learns to tolerate his presence. If only for Edelgard’s sake, because he seems to be the only other person besides Byleth that she seems to enjoy spending time with. Byleth has toned down her outright staring to side-eyeing.

Dimitri calls Edelgard ‘El’ one day, after having heard Byleth use the nickname a few times before, and the silence that follows after is awkward. He immediately tries to apologize when their attentions lock onto him. “I’m sorry! I didn’t know that it was a special name for you both!”

Edelgard reassures Dimitri, “It’s fine.” After a moment of internal debate, she tells him, “I suppose I don’t see the harm in allowing you to use the nickname as well.” They settle that matter quickly, but Byleth still eyes him whenever he calls her by it. Edelgard thinks Byleth would be glaring if she could.

Edelgard teaches him to dance at one point while Byleth stands on the side. Byleth tells Dimitri that she might have to do something if he kept stepping on Edelgard’s feet. Her typical bland tone makes the warning sound more threatening than it really is, and he frets as he tries to pay closer attention to where he steps. Edelgard laughs and forces him to look up at her, saying that it would be poor dancing if he were to always be looking at his feet.

The pattern of Dimitri just watching them spar is broken when he asks to join in on the training sessions. He had shyly asked them the first time. “Um...would it be okay if I joined in today?”

Surprised by his sudden request, Edelgard pauses for a moment before looking over to see Byleth nod in deference to her. “I don’t see why not. What would you like to practice?” She leads him over to the rack to show him what weapon choices are there.

“Probably a sword or lance.” Dimitri fidgets with his sleeves, clearly wanting to say more.

Edelgard watches him, gauging. “Do you want Byleth to teach you?”

Relieved that she asked the question he could not, Dimitri looks at her hopefully. “Yes, if that’s not too much to ask.”

They both turn to look at Byleth, who decides to entertain him when she sees Edelgard smiling encouragingly at her. “Okay. Show me what you can do first.” Byleth pits the two of them against each other so that she can watch him. She tells them to go two rounds, once with a sword and then once with a spear.

Byleth observes him closely, taking note of every step he takes and the few swings he makes. He is decent with a spear, but his swordplay is shoddy. Edelgard pushes him around with her axe, and he reminds Byleth of a mouse, scurrying away from Edelgard’s axe rather than meeting her swings. “If you meet more of her swings instead of retreating every time I can get a better read on your abilities,” Byleth tells him.

Byleth has them go another round with him using a spear before she steps in. “Let me see your stance again.” He is steady, but she moves his hands to be properly spaced while holding the spear. “Attack me.” He has considerable strength, but his thrusts are not precise and he expends too much energy with each swing of the spear. She critiques him as such, and Dimitri tries his best to follow her instructions.

They continue to work on his spear work every day, either sparring with Byleth or with Edelgard. Byleth thinks that he would probably make a good cavalry unit eventually, but then she wonders if someone like him would ever be able to fight on the frontlines.

Edelgard asks him about practicing his sword as well, but he seems too intimidated to do anything with a sword besides hit a striking dummy. It takes a long time, but he eventually finds the confidence to go one round with Byleth. She holds back at Edelgard’s request, and lets him gather his nerves. She waits and allows him to come at her when he is ready, but he is still disarmed and ‘dead’ almost immediately.

Despite the quick defeat, it does not seem like Dimitri is discouraged. There is admiration in his eyes as he glances at Byleth and then back at the ground. “I wish I was as strong as you are, Byleth.”

Byleth does not respond to his praise, unmoved by his display of regard for her skill, and merely asks him if he wants to go another round.

Dimitri comes earlier than normal the next day, and they wait together in the hallway outside Edelgard’s room. His voice cuts through the silence between them. “Edelgard mentioned before that you wanted to become a knight.”

“Yes, so that I can keep protecting El.” Byleth sees Dimitri turn towards her in her peripheral.

“Byleth.” His tone is firmer than Byleth has ever heard it, and it draws a hum from her. “I promise to become a great knight and leader so that I can help you protect her!”

Byleth finally turns to quietly stare at him like always, but for the first and only time she could recall since they met, his eyes meet hers resolutely without flickering away when their gazes meet. It is enough for her to nod at him, which he seems to take as her approval if the smile on his face is anything to go by as he turns back to face the other wall again.

They wait in silence again until Edelgard comes out of her room, and when she greets them with a smile, Byleth silently reaffirms her own vow to stay beside Edelgard.

**Author's Note:**

> @yyunica on Twitter


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